When comparing Ceylon vs F# (via FunScript), the Slant community recommends Ceylon for most people. In the question“What are the best languages that compile to JavaScript? ”Ceylon is ranked 14th while F# (via FunScript) is ranked 32nd. The most important reason people chose Ceylon is:

The compiler prevents you from using a potentially null variable, unless you check it is not null. Ie. it forces you to check a potentially null value before using it.
The type system is strict, but flexible, allowing union and intersection of types, covariant and contravariant types, reified types, etc.
Type inference and union types allows a dynamic programming style, close of JS spirit.

Pros

Pro

The compiler prevents you from using a potentially null variable, unless you check it is not null. Ie. it forces you to check a potentially null value before using it.The type system is strict, but flexible, allowing union and intersection of types, covariant and contravariant types, reified types, etc.Type inference and union types allows a dynamic programming style, close of JS spirit.

Pro

Designed from the start to generate JavaScript

It brings type safety to JS, allowing to define interfaces to existing JS APIs, yet using the dynamic keyword for flexible calls in the JS ecosystem.

Pro

Excellent IDE support

Ceylon has reified generics, so it doesn't loose the type of collections at runtime. This makes autocompletion, debugging, etc. first-class. The Eclipse plugin makes it a full-fledged Ceylon IDE, and an IntelliJ IDEA plugin is in the works.

Pro

Great tutorial

Gavin King, main author of the language, has a great, clear technical writing style, making understandable difficult concepts like variance or sound type system.

Pro

Excellent documentation

The language specification is very complete and up to date; also, the language module is very well documented.

Pro

Javascript interoperability

Ceylon has special language-level support for interoperation with dynamically typed languages like JavaScript, and its module system even interoperates with npm.

Pro

Easy to learn even if you don't have prior programming experience

Ceylon is indeed fairly easy and readable. Of course those ones who know OOP and a bit of functional programming concepts will feel almost at home right from the start.

Pro

Generate HTML

HTML generation is supported right in the SDK.

Pro

Same code in backend and frontend

If you don't use platform-specific features, you can reuse the same code in your backend server (be it in Java or JavaScript) and in your client-side browser code, for example for storing data, validating input etc.

Pro

Easier transition from other paradigms

Since F# is not a purely functional language, it lends itself to being more easily picked up by programmers that have experience with other paradigms.

Pro

Concise syntax

F#'s syntax tends to be terse while remaining very readable and easy to understand without being a chore to write.

Pro

Runs on the CLR

Since F# runs on the Common Language Runtime or CLR, it has access to the entire .NET Framework, as well as libraries written in other .NET languages such as C#, VB.NET, and C++/CLI.

Cons

Con

Lack of physical or electronic books

We should hope Red Hat or anyone interested would take the time and write one. That would strengthen the maturity of the language, but Ceylon is rapidly developing which can make the author's efforts futile because his or hers work will become obsolete soon.The second hindrance is, of course, popularity of the language which can't give much to the pockets of the author (however, Dart's unpopularity at start didn't prevent it to have a lot of printed material, but that's Google's child, we know).

Con

Currently has large runtime

Ceylon 1.2 needs a language runtime of 1.55 MiB, and the Collection library adds another 370 KiB. That's a lot for the Web...Now, this has to be put in perspective: if you use Ceylon to make a web application, these files will be loaded once, then cached by the browser (that's not casual browsing).Moreover, most servers compress such resource, and the numbers become respectively 234 KiB and 54 KiB, which is more reasonable...

Con

Not really cross platform

Though the community sites are touting F# can be cross platform through use of Mono, the reality is that it is more of a hack to replay on larger mono applications in production.